Little change to 90L; flow of oil southwards towards Loop Current shuts off

An extratropical low pressure system a few hundred miles northeast of the Bahamas (90L), has changed little over the past day. (For those of you who were wondering, a discussion of what an "Invest" is can be found in the Tropical Cyclone FAQ). This low has the potential to develop into the season's first depression or subtropical storm, and could be a threat to the Southeast U.S. coast by Tuesday or Wednesday. The SHIPS model predicts that shear will be in the high 30 - 40 knot range through Tuesday, though. The high shear combined with the large amount of dry air to 90L's west seen on water vapor satellite loops will greatly hamper transition of this system to a subtropical storm. This system is expected to move slowly north and then northwestward towards the Southeast U.S. coast over the next three days, and could bring 20 - 30 mph winds and heavy rain to the coast of North Carolina by Tuesday night. Most of the models indicate that Wednesday will be when 90L gets closest to the coast, with a position just off the North or South Carolina coast. All of the major models currently indicate that 90L will not make landfall, but will move slowly northeastward out to sea late next week as a trough of low pressure moving across the Eastern U.S. picks up the storm. While the storm will initially form in a region of high wind shear and be entirely extratropical, it will move into a region of lower wind shear in a gap between the polar jet stream to the north and the subtropical jet stream to its south by Wednesday. At that time, the low will be positioned near the warm waters of the Gulf Stream, and will have the opportunity to develop a shallow warm core and transition to a subtropical storm. The counter-clockwise flow of air around this low will probably lead to offshore winds over the oil spill region Tuesday through Wednesday, keeping oil away from the coasts of Alabama and the Florida Panhandle, but pushing oil southwards towards the Loop Current. Wunderbloggers Weather456 and StormW have more detailed discussions of the potential development of 90L.

Figure 1. Visible satellite image of 90L this afternoon.

Heavy rainfall threat for Haiti diminishesMoisture is expected to increase across most of the Caribbean next week, leading to seasonally heavy rains across much of the region. A concentrated tropical disturbance capable of bringing dangerous flooding rains to Haiti is no longer being indicated, but the normal heavy rains that we can expect this time of year will likely begin affecting the island over the next several weeks.

Flow of oil southward towards the Loop Current shuts offLight southeast to east winds are expected to blow over the northern Gulf of Mexico today through Monday, resulting in potential oiling of Louisiana shorelines from the mouth of the Mississippi River westward 150 miles, according to the latest trajectory forecasts from NOAA. These winds shut off the flow of oil southwards towards the Loop Current, as seen in the latest SAR satellite imagery (Figure 2). However, winds will shift to offshore out of the north or northeast Tuesday and Wednesday, due to counter-clockwise flow of air around the approaching 90L storm. This wind direction change should give some relief to the hard-hit Louisiana coast. If 90L becomes strong and lingers off the Southeast U.S. coast for several days, a significant amount of oil could get pumped into the Loop Current late next week.

Oil threat to the Keys uncertainSatellite imagery from today's pass of NASA's Terra satellite and the European Envisat satellite were inconclusive as to the presence of oil in the Loop Current. It is likely that the oil has dispersed significantly over the 500-mile course it has taken from the site of the Deepwater Horizon blowout. I expect some oil is close to completing the full loop of the Loop Current and is now headed east towards the Keys, as depicted in the "Uncertainty" area in the latest NOAA 72-hour offshore trajectory forecast. If this estimate is correct, the Keys could see oil as early as Wednesday. However, this is not a sure thing. As I discussed in my post Wednesday, the Loop Current is very unstable right now, and is ready to cut off into a giant clockwise-rotating eddy, an event that occurs every 6 - 11 months. This event could occur today or tomorrow, in which case the ribbon of southwestward-moving oil would turn due west and then north, eventually winding up back near the site of the Deepwater Horizon blowout. Roffer's Ocean Fishing Forecast Service has a nice discussion on the possibility of the Loop Current cutting off into a Loop Current Eddy, and they note in today's discussion that there appears to be a developing eastward flow of water directly from the Yucatan Peninsula to the Florida Keys. Keep in mind, though, that during the first month that a Loop Current Eddy forms, it exchanges a considerable amount of water with the Loop Current. Even if a Loop Current Eddy forms today, I still expect we will see some oil make the turn eastward and flow past the Florida Keys by Wednesday. My guess is that the oil will be too thin and scattered to cause significant problems in the Keys, but there is great uncertainty on this.

Quoting Levi32:90L is struggling with the massive amount of dry air coming into its southwest quad. This is making it difficult for convection to take advantage of the lessened wind shear and form closer to the COC. The current low center is backing away SSW, but we've seen this twice before now. 90L is not about to just go away, not as long as there is an upper feature supporting it aloft.

90L is still baroclinically driven. A tropical system looking like this would be in pretty bad shape, but we've already gone through this twice and 90L has no problem forming new lows under the area of upper divergence and dumping the old dried-out ones into the low-level flow that leads to their death. We should see another new low try to form to the north of the current one sometime overnight tonight.

Correct. The NHC 8:05 Discussion said that a new low is developing under the strongest convection. I'm sure there will be many more low replacements to come.

A BROAD DEEP LAYER TROUGH IS OVER THE WESTERN ATLANTIC. AN UPPER LEVEL LOW IS EMBEDDED IN THIS TROUGH...NOTED ON WATER VAPOR IMAGERY...AND SUPPORTS A 1007 MB SURFACE LOW CENTER NEAR 24N70W. A SURFACE TROUGH CROSSES THE LOW CENTER ALONG 29N68W 24N70W 21N70W. MARINE OBSERVATIONS NEAR THE LOW CENTER INDICATE 8 FT TO 12 FT SEAS. GALE FORCE WINDS ARE DEVELOPING NORTHEAST OF THE LOW CENTER FROM 25N TO 32N BETWEEN 65W AND 70W. THIS SYSTEM IS BEEN FURTHER ENHANCED BY THE FORMATION OF A UPPER LEVEL LONGWAVE SOUTHWEST OF THE SYSTEM. WHILE THE CURRENT LOW SHIFTS SOUTHWARD...SATELLITE IMAGERY SUGGESTS THAT A SECOND LOW IS DEVELOPING TO THE NORTH OF THE CURRENT LOW AND IT IS EXPECTED TO BE ADDED TO THE SURFACE UNIFIED MAP BETWEEN 24/0000 UTC AND 24/0600. COMPUTER MODELS SUGGEST THE SECOND LOW WILL STRENGTHEN AND MOVE NORTHWEST TO NEAR 30N71W OVER THE NEXT 24 HOURS. MOST OF THE CONVECTION IS FOUND EAST OF THE SYSTEM FROM 19N TO 32N BETWEEN 55W AND 71W. MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE NORTH EAST OF THE LEEWARD ISLANDS FROM 17N TO 24N BETWEEN 57W AND 62W.

This is quite reminiscent of prior year seasons... usually in May or June, there is a low close to South Carolina that storm watchers on here all gaggling about ... these tend to be near-misses and don't develop but give us a sense that the season is about to take off.

They say the response has been too slow and their anger is now beginning to manifest itself in different ways.

the response is still slow as heck.. I mean honestly waiting an entire week to just try something is really slow.. why not just seal the dam thing already with there mud method, instread of waiting 7 days to do so.

90L is struggling with the massive amount of dry air coming into its southwest quad. This is making it difficult for convection to take advantage of the lessened wind shear and form closer to the COC. The current low center is backing away SSW, but we've seen this twice before now. 90L is not about to just go away, not as long as there is an upper feature supporting it aloft.

90L is still baroclinically driven. A tropical system looking like this would be in pretty bad shape, but we've already gone through this twice and 90L has no problem forming new lows under the area of upper divergence and dumping the old dried-out ones into the low-level flow that leads to their death. We should see another new low try to form to the north of the current one sometime overnight tonight.

90L is actually doing better than I thought it would by now, I place odds of development at 35%.. up from yesterday. Again I ask, WUmail me if your at all interested in what I have to say about this system (I'll probably say that for the rest of the year) and also, come June 1st i'll be starting a daily Tropical Weather discussion blog.

Hello Teddy. I havn't been updating my blog lately but when the season starts I'll post much more often. I'm also interested in reading your blog.

Quoting AussieStorm:Looking at this Loop. One can see the COC/LLC clearing out to the south then the main body of convection clearing out to the north then dying off. A smaller firing of convection can be see almost due west of the COC/LLC.In my honest opinion, 90L wont be around for much longer, but I maybe wrong.....I'm just sayin...

It seems to go in cycles as the intensity models have been showing the past few days. Tonight we shall see if convection can redevelop...

90L is actually doing better than I thought it would by now, I place odds of development at 35%.. up from yesterday. Again I ask, WUmail me if your at all interested in what I have to say about this system (I'll probably say that for the rest of the year) and also, come June 1st i'll be starting a daily Tropical Weather discussion blog.

HORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...-- Changed Discussion --WILL BE WATCHING THE PROGRESSING OF AN AREA OF LOW PRES THAT ISPRESENTLY DEVELOPING NE OF THE BAHAMAS THROUGH THE SHORT TERM.MODELS CONTINUE TO LIFT THE VERTICALLY STACKED LOW PRES AREATOWARD THE AREA BUT KEEP THE LOW WELL OFFSHORE. MODELS COMING INTOBETTER AGREEMENT WITH THE LOW STALLING ABOUT 250-300 MI SE OF CAPELOOKOUT TUE NIGHT AND WED. MAIN IMPACT FROM THIS SYSTEM WILL BEACROSS THE MARINE AREAS AS WELL AS BUILDING SURF AND INCREASINGTHREAT OF RIP CURRENTS ALONG THE COAST. AT THIS TIME ANY THREAT OFOCEAN OVERWASH LOOKS MINIMAL BUT WILL CONTINUE TO MONITOR THEPROGRESS OF THE SYSTEM. THERE REMAINS SOME UNCERTAINTY REGARDINGTHE AMOUNT OF MOISTURE THAT PUSHES ACROSS ERN NC AND WITH THEMODELS TRENDING FARTHER OFFSHORE AND WE MAY NOT SEE AS MUCH RAINAS PREVIOUSLY THOUGHT. WILL KEEP CHANCE TO SLIGHT CHANCE POPSTHROUGH MOST OF THE PERIOD...HIGHEST NEAR THE COAST. BY SUN NIGHTTHE LOW PRES SYSTEM BEGINS TO DRIFT SEWD AS UPPER N/NWLY FLOWINCREASES IN RESPONSE TO AN UPPER LOW RETROGRADING INTO THECANADIAN MARITIMES. TEMPS NEAR TO SLIGHTLY ABOVE NORMAL EXPECTE

As all discovery channel nerds knew ahead of time, the dome had zero chance whatsoever of success at that depth when dealing with a blown well spewing methane and oil.

The dome became bouyant due to a combination of factors, as myself and countless others predicted, because methane hydrate crystals condensed inside the dome, blocking off it's funnel tube, and making it buoyant because methane hydrate is less dense than water (as is oil).

Because methane hydrate is not really "ice", but is a mineral formed from water and methane, it doesn't simply "melt" at those pressures even if you add heat or chemicals. It is a crystal structure, just like quartz or diamond, which forms under pressure. Then, once formed, it can stay that way even at surface pressures, at least temporarily.

The smaller "top hat" approach was a step in the WRONG direction, because it has all the same problems, and its "fixes" don't actually work, and because it is less massive than the "dome" it would buoy up anyway, though this effect would be offset some by the smaller volume.

This "junk shot" involving mud and debris is not going to work either, because the materials they have suggested is not heavy enough.

They need to use iron or lead shot of two sizes (the smaller size balls machined to fit in the empty space between ideal stackiing of the larger size,) and dump this down the pipe. Anything else will not be dense enough to work, and will just get pushed back out of the way.

Actually, I'd prefer molten lead or iron, but I have no idea how they'd get it down there...

How about one of the Super Fast-Setting Epoxy's, injected in 2 parts through a nozzle that blends them just before they enter the casing?

I dont' know where the funds would come from, but instead of dredging, which doesn't help vs hurricanes anyway, why don't they buy like train loads of gravel and other aggragate and use that to make these levees? At least its denser and obviously heavier grain so it sticks vs hurricanes, and it still serves the purpose of blocking the oil...

Just seems to me if you are gonna do something, may as well do it right.

The wetlands need the tidal water that flushes in and out of them naturally. I think the idea behind sand levees is that they could be easily removed to restore the natural flow once the oil is gone.

I understand that, but if they dredge it's just gonna make the intrusion of salt water that much worse in future years.

Unless someone plans on literally making a solid wall of levees around lousiana some time soon. Which has been proposed but never taken seriously.

It's kinda catch 22 right now, as I see it.

I got a better idea. I saw some (water)inflatable temporary levee/sandbagging products which were demonstrated on the weather channel a year ago or so. I guess these were maybe 4 ft in diameter or so. The deal is you fill them with water and they act as a storm barrier or flood barrier for a localized area.

These would be much faster and less damaging than dredging. Basicly just put them in the water and fill them with water, and stack them two or 3 high till you have a barrier that is above water and would keep out the oil....Works like sandbagging, but without the sand or backbreaking work. Just set up the tube and pump it full of water...you could make a pyramidal wall of them, like 3 wide at the base, then 2 then 1 on top, etc.

OK. BUT...filled with water, they would be the same weight as water, and float away. Fill them with some heavy fluid, like oilwell mud (which is basically Barytes), and then you could sell this mud back to BP!

Looking at this Loop. One can see the COC/LLC clearing out to the south then the main body of convection clearing out to the north then dying off. A smaller firing of convection can be see almost due west of the COC/LLC.In my honest opinion, 90L wont be around for much longer, but I maybe wrong.....I'm just sayin...

BY THE END OF THE NEW WORK WEEK MODELS CONTINUE TO SUGGEST THEPOTENTIAL FOR A SIGNIFICANT HEAVY RAINFALL EVENT AS BROAD AREA OFLOW PRES FORMS ACROSS THE SW CARIBBEAN. BULK OF THE MOISTURE LOOKSTO AFFECT THE DOMINICAN REPUBLIC BUT CAN`T RULED OUT SOME MCSACTIVITY AFFECTING PARTS OF THE ISLAND. A SFC TROUGH WILL DEVELOPLATER IN THE WEEK MOST LIKELY INDUCED BY THE LARGE UPPER TROF FCSTTO EVOLVE ACROSS THE ATLC. GIVEN THE AMPLITUDE OF THE UPPER TROFAND EXTREMELY HIGH PWAT VALUES FCST THIS SITUATION WILL NEED TO BEMONITORED VERY CLOSELY ESPECIALLY GIVEN THE CONSISTENCY OF THEMODELS WITH THIS POTENTIAL EVENT.

Quoting HaboobsRsweet:that is what I have been saying for a week. yes they did well picking up on a feature but had no handle on that feature. They have jumped all over the place. That happens in transition season. they will get better in a few weeks.

that is what I have been saying for a week. yes they did well picking up on a feature but had no handle on that feature. They have jumped all over the place. That happens in transition season. they will get better in a few weeks.